My guess would be that your grandfather would simple seize to exist and you would never be born, but thats just in one of many many diffrent multiverses that all play out diffrently playing out all the diffrent depending on the choices we make.

Bless the Maker and His water.
Bless the coming and going of Him.
May His passage cleanse the world.
May He keep the world for His people.

My guess would be that your grandfather would simple seize to exist and you would never be born, but thats just in one of many many diffrent multiverses that all play out diffrently playing out all the diffrent depending on the choices we make.

But if you're grandfather will seize to exist you will never be born and thus not be able to travel back in time to kill him

If you went back in time and killed your grandfather, who would kill your grandfather?

Post more lets see all head exploding/world destroying ideas

It's called the Grandfather Paradox. The most common hypothetical result is that there is a fork in reality, whereby a new reality branches off and the reality where you exist as a descendant of your grandfather ceases to exist as a reality.

Time travel is definitely a head exploding idea. The possibilities are endless.

The theory I hear most often is that time travel is only possible in one direction, namely forward.

There are other theories (sorry for the lack of source material, might add some later, I'm sure there's loads of decent (and loads more crappy) stuff available by googling it)

-A certain time machine should make time travel possible to the past, but not earlier than the creation of the machine itself.

-According some physicists (including hawking) time travel would only be possible to the future, for example by moving in an object at a speed close to the speed of light. When moving near this speed, time would slow down to prevent from moving faster than light speed (Which is, according to people a lot smarter than me, physicly impossible). "If I sit in a train that moves at the speed of light, and I walk to the front of the train, I would be moving faster than the speed of light." This means that, the higher your velocity, the slower time will move (This is a proven fact: see http://en.wikipedia.org/wiki/Time_dilation if you want more details.).

This means 2 things:

1.apparently we will never be able to go back in time and kill our forefathers (or hitler for that matter).
2. I watch too much discovery channel

What if your future self would come visit you, and give you the plans for a time machine, later on you'd travel back yourself and give your past self the plans. Who had created the first plans for that time machine?

You didn't specify when you killed your grandfather, an easy answer would be, your grandfather got killed by an unsub, you'r dad/mom has already been born and then you got born, wondering how ur grandfather died untill the day you realize it was you who killed him

You didn't specify when you killed your grandfather, an easy answer would be, your grandfather got killed by an unsub, you'r dad/mom has already been born and then you got born, wondering how ur grandfather died untill the day you realize it was you who killed him

If Pinnocio tells you his nose will grow, what happens?

Lol never heard the Pinnocio one before, clever.
It's basically the same as this old one:

The following statement is a lie.
The previous statement is the truth.

---------- Post added 2011-01-29 at 12:26 PM ----------

Originally Posted by jvbastel

The theory I hear most often is that time travel is only possible in one direction, namely forward.

There are other theories (sorry for the lack of source material, might add some later, I'm sure there's loads of decent (and loads more crappy) stuff available by googling it)

-A certain time machine should make time travel possible to the past, but not earlier than the creation of the machine itself.

-According some physicists (including hawking) time travel would only be possible to the future, for example by moving in an object at a speed close to the speed of light. When moving near this speed, time would slow down to prevent from moving faster than light speed (Which is, according to people a lot smarter than me, physicly impossible). "If I sit in a train that moves at the speed of light, and I walk to the front of the train, I would be moving faster than the speed of light." This means that, the higher your velocity, the slower time will move (This is a proven fact: see http://en.wikipedia.org/wiki/Time_dilation if you want more details.).

This means 2 things:

1.apparently we will never be able to go back in time and kill our forefathers (or hitler for that matter).
2. I watch too much discovery channel

Velocities don't stack like that when moving at relativistic levels.
Even at everyday velocities they don't stack.. it's just so close it's unnoticeable.

---------- Post added 2011-01-29 at 12:30 PM ----------

Here's an interesting thing to think about. If a spaceship is traveling at 95% the speed of light above the earth and fires a laser straight forwards (in the same direction they're traveling), the laser will be traveling at the speed of light away from them, but will also be traveling at only slightly faster than the speed of the ship relative to the stationary observer on the ground.

If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the Mighty One... now I am become Death, the Destroyer of Worlds.